No idle after new tii fuel pump

[Ensign]

My tii fuel pump was starting to make unusual noises so I replaced it with the Bosch pump made for the 5 series.  The car runs fine with the new pump except that the idle was so slow, after installing the new pump, that the engine would stall. I adjusted the idle at the tuna can and that worked, but it didn’t make sense to me that I would have to do that. I removed the banjo bolt on the K-fisch to see if the screen filter was dirty, but it was clean. I started the car to check for leaks and the engine was idling around 1700 rpm after warm-up, so I dialed back the idle on the tuna can thinking that something I did “fixed” the problem. Basically I returned the idle screw to the position before the new pump was installed. I took the car for a test drive and it stalled at the second stop sign (about 2 minutes after starting). So I was back where I started. Again, the engine runs fine and accelerates smoothly, but won’t idle unless I make a significant adjustment to the idle speed screw.  I would leave it except for the fact that the procedure with the banjo bolt seemed to temporarily ‘fix” the problem.  Any thoughts…?

Thanks in advance,

Tony

[tzei]

Hoses & fitting good ’n tight? El. connections alright?

Alt puts out what it should?

[Son of Marty]

Fuel pressure?

[Ensign]

18 minutes ago, tzei said:

Hoses & fitting good ’n tight? El. connections alright?

Alt puts out what it should?

Thanks for the reply. Yes, everything seems to be in order.

 

17 minutes ago, Son of Marty said:

Fuel pressure?

I'm not sure. I don't have a gauge. The only thing I could do is use the Mike Macartney method of measuring the amount of fuel delivered in 30 seconds. Would the engine run properly otherwise, if the fuel pressure was too low?

Thanks for your idea.

[tzei]

Did it work right with old f/pump exept the noise(s)?

If yes then put it back - idles normally?

Yes - pump issue…

54 minutes ago, Ensign said:

everything seems to be in order.

Now that’s the thing: ”seems”.

 

No - vac leak.

 

or maybe cold start injector leaks and it goes just a tad too rich? AFR meter would be nice… does it lean and die or go pig rich and die.

[SydneyTii]

Have a quick look at the fuel pressure maintenance valve on the back of the Kuglefischer head.

[Ensign]

1 hour ago, tzei said:

Did it work right with old f/pump except the noise(s)?

yes it did, but I'm not going to give up on the new pump just yet

 

1 hour ago, tzei said:

or maybe cold start injector leaks and it goes just a tad too rich? AFR meter would be nice… does it lean and die or go pig rich and die.

I swapped it out with a spare with no change.

[Ensign]

19 hours ago, SydneyTii said:

Have a quick look at the fuel pressure maintenance valve on the back of the Kuglefischer head.

Thanks for the suggestion! I had a spare that had been cleaned and tested, so I tried it and things have improved considerably.  Thanks again.

Edited September 5, 2023 by Ensign
typo

[JohnS]

I assume you cleaned out the gas tank and made sure the screen on the in-tank fuel pickup is in place and clean?  My '74 used to stall and it turned out that the screen on the fuel pick-up was all crusty and clogged.

Edited September 5, 2023 by JohnS

[Son of Marty]

All Tii owners need to have a fuel pressure tester, Harbor Fright has one for under 40 bucks with coupon. The fuel delivery test is for volume not pressure. The Tii k-fish is just a fuel pressure multiplier and it's calibrated for a 29 psi input. Fuel pressure is like blood pressure and how long does it take the nurse to check your b/p when your at the doctor?